Chairman of the Joint Chiefs of Staff Martin Dempsey said the United States has three big risks in combating ISIS, and that the campaign will take "several years" to complete.

Speaking at a Senate Armed Services Committee hearing Tuesday, Dempsey, who earlier mentioned sending ground troops to Iraq could be a possibility if the president's campaign to defeat the Islamic State of Iraq and Syria (ISIS) fails, said a major risk in combating ISIS would be a coalition falling apart over time.

"The three big risks that I would mention to you are: if the government of Iraq fails to become inclusive, and though the signs are promising they haven't yet fully delivered," Dempsey said.

The general added a coalition would need endurance, because any campaign to defeat ISIS would take several years.

"Second, if a coalition forms but doesn't have endurance because this is going to take several years," Dempsey said.

The last risk Dempsey mentioned was the Iraqi government not establishing control of areas recaptured from ISIS to prevent retribution from those who collaborated with ISIS militants.

"The third risk is retribution. When we encourage and assist the Iraq security forces to regain lost territory we have to be alert for the fact that unless the government of Iraq is there to embrace the people and ensure that they work together there could be retribution on the part of those who may have been seen as complicit with ISIL."

"So we have some challenges ahead. We are open-eyed to them, but I think we have a good campaign plan."

Andrew Kaczynski is a political reporter for BuzzFeed News and is based in New York.